Removable or hinged component for covering openings in the fuselage of an aircraft

ABSTRACT

A component for cladding apertures in the fuselage of an aircraft is to be of lighter weight and more corrosion resistant as compared with known claddings. The component is manufactured of carbon fibre reinforced curable synthetic resin and comprises a base layer (2) onto which U-profiles (4, 4&#39;) and L-profiles (5, 5&#39;) are placed in spaced apart interrelationship, which during the manufacture are held in place by a grid (14) comprising angular bridge members. A vacuum foil (7) is applied over this assembly and is adhesively bonded along the edges of the base layer (2&#39;) to the supporting surface (1). The space between the vacuum foil (7) and the supporting surface (1) is evacuated and curing proceeds at an elevated temperature and pressure. After complete curing the vacuum foils (7) and the grid (14) are removed.

BACKGROUND AND FIELD OF THE INVENTION

The invention relates to a removable or hinged component for coveringapertures in the fuselage of an aircraft, e.g. covering or service portsfor aggregates such as an auxiliary gas turbine or air-conditioningplant. In the case of failures and servicing of the aggegates, thecovering must be capable of rapid removal. This involves usuallyself-supporting shells of large surface area which are fitted to thefuselage at only a few localities (e.g. hinges) and which are locked toone another or to the fuselage by fast-acting fasteners. Thesecomponents are at present made of aluminium having a wall thickness of afew millimeters serving as outer layer and numerous reinforcement ribsfor accommodating the closure forces, forces arising from theaerodynamic resistance of the cladding and of pressures resulting frommalfunction of the installed aggregates (fire, explosion). On occasioncomposite materials comprising a light core and fibrous webs have alsobeen employed. In order to save weight, the aluminium skin is of reducedwall thickness in localities of reduced load. For that purpose chemicaletching is employed or one sheet is adhesively bonded onto a furthersheet having cut-away regions.

GENERAL DESCRIPTION OF THE INVENTION

It is an object of the invention to provide a component for the claddingof apertures having a substantially reduced weight, as compared withknown claddings and having corrosion-resistance, so that little or nomaintenance is needed.

Further or alternative objects will become apparent from what follows.

According to the invention a a component as set out in the openingparagraph comprises a base layer on which, spaced apart, a plurality ofpreferably mutually parallel U-profiles is provided, the base portionsof which extend transversely to the base layer and one limb of which isflush with the base layer and that at the transition between the baselayer and the base portion which faces away from the limb an L-profileis provided in each case, the base layer, U-profile and the L-profilebeing composed of fibre reinforced, e.g. carbon fibre reinforced fullycured synthetic resin.

In a first embodiment of the invention the limbs of at least somesuccessive U-profiles are directed to face the limbs of an end profile.

In a second embodiment of the invention the limbs of adjoiningU-profiles face each other.

In a third embodiment of the invention a cover layer is applied onto thefree-standing limbs of the U-profiles, composed of fibre reinforced,e.g. carbon fibre reinforced fully cured synthetic resin.

The first process for manufacturing the component according to the firstembodiment, according to the invention, provides that the base layer isapplied onto a large area supporting surface having a configurationwhich in the longitudinal and transverse directions corresponds to thedesired configuration of cladding for the aperture, that the U-profilesare applied onto the supporting surface, that thereafter the L-profilesare applied onto that side of the base portion of the inner U-profileswhich faces away from the limbs, that onto the U-profiles a grid framedby a frame is applied which holds the U-profile and the L-profilestogether, that in a manner known per se a vacuum foil is applied overthe structure formed in that manner and is adhesively bonded along theedges of the base layer to the large area supporting surface, whereuponthe space between the vacuum foil and the large area supporting surfaceis evacuated and complete curing takes place at elevated temperature andpressure, whereafter the vacuum foil and the grid are removed.

The second process for the manufacture of the component according to thesecond embodiment, in accordance with the invention, provides that thebase layer is applied onto a large area supporting surface, theconfiguration of which corresponds in the longitudinal and transversedirections to the desired configuration of the cladding for theaperture, that onto a subsequently removable core of rectangular crosssection on both sides of the narrow sides of the core the U-profiles areapplied and the unit formed by the U-profiles including the core is laidonto the base layer, the core being matched to the configuration of thelarge area supporting surface in the longitudinal direction, thatsubsequently the L-profiles are fitted on both sides of the U-profiles,that a vacuum foil is applied over the structure formed in the aforesaidmanner and is adhesively bonded along the edges of the base layer to thelarge area supporting surface, whereafter the space between the vacuumfoil and the large area supporting surface is evacuated and completecuring takes place at elevated temperature and pressure followed by theremoval of the vacuum foil and the core.

The third process for the manufacture of the component according to thefirst or second embodiment in accordance with the invention providesthat, after the production of the component according to the first orsecond embodiment a closed rubber bag having an inlet nipple is insertedinto each of the spaces between the U-profiles, that a covering layer offibre-reinforced curable plastics is applied onto the free-standinglimbs of the U-profiles and a vacuum foil in the form of a bag is drawnover the entire assembly, the inlet nipples projecting from the vacuumfoil and being adhesively bonded thereto in an airtight manner in theregion of contact, whereafter the space between the vacuum foil and therubber bags is evacuated, and a complete curing of the covering layertakes place at elevated temperature and pressure followed by the removalof the vacuum foil and the rubber bags.

Epoxy resin, phenolic resin or polyamide resin can be used as theplastics.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and details of the invention will in the following beexplained with reference to the drawings. There is shown in FIG. 1 afirst embodiment of the invention in cross section, FIG. 2, adiagrammatic view of a grid surrounded by a frame serving for themanufacture, FIG. 3, a second embodiment of the invention in crosssection and FIG. 4 a third embodiment of the invention in cross section.

DESCRIPTION OF SPECIFIC EMBODIMENTS BY WAY OF EXAMPLE

In FIG. 1, 1 denotes a large area supporting surface, the configurationof which in the longitudial and transverse direction is adapated to thedesired configuration of the cladding. In the illustrated example thesupporting surface 1 extends rectilinearly in the transverse direction,whilst in the longitudinal direction it may for example be of circularlyarcuate configuration. A base layer 2 of fibre reinforced curablesynthetic resin is applied onto this supporting surface. The supportingsurface 1 is coated with a suitable agent to avoid adherence of the baselayer 2. Onto the base layer 2, in spaced apart relationship a pluralityof U-profiles 4 are placed, the limbs 6a of which are directed to facethe limbs 6A' of a terminal profile 4'. This is followed by theapplication of one L-profile 5 or 5' each of fibre reinforced curablesynthetic resin along the transition between the base layer 2 and thebase portion 6 of the U-profile 4 on that side of the base portion 6 or6' which faces away from the limbs 6A. As shown in FIG. 1, a grid 14,which as illustrated in FIG. 2 is composed of a frame 15 with handles 16and angular bridges 19 held between the longitudinal sides 17, 18, thetransverse side 20, 21 being connected to struts 22, 23, is placed ontoeach of the U- and L-profiles 4, 4', 5, 5'. In the illustrated conditionof use of the grid as shown in FIG. 1, the grid rests with its struts22, 23 and the horizontal limbs 24 of the bridge members 19 on the upperlimbs 6A, 6A' of the U-profiles 6, 6' and by means of the transversestruts 20, 21 as well as the vertical limbs 25 of the bridge members 19,it engages behind the L-profiles 5, 5' whereby the profiles 4, 5, 4', 5'are held in a fixed position on the base layer 2. A vacuum foil 7 isplaced over the structure formed in that manner and is adhesively bondedalong the edges of the base layer 2 onto the supporting surface 1. Thespace between the vacuum foil 7, the supporting surface 1, the grid 14,the base layer 2 and the profiles 4, 5, 4', 5' is then evacuated. Thisis followed by complete curing in an autoclave at a temperature of 120°to 315° C., preferably 160°-282° C. and more preferably 170°-200° C. andat a pressure of 4 to 10 bar, preferably 5 bar. After completion ofcuring, the vacuum foil 7 and the grid 14 are removed.

In FIG. 3, 1 denotes a large surface supporting surface, as in FIG. 1,the configuration of which in the longitudinal and transverse directionsis adapted to the desired configuration of the cladding. In theillustrated example the supporting surface 1 is rectilinear intransverse direction whilst in the longitudinal direction it may forexample be of circular arcuate shape. A base layer 2 of fibre reinforcedcurable synthetic resin is applied onto this supporting surface. Thesupporting surface 1 is coated with a suitable agent to avoid adhesionof the base layer 2. A U-profile 4 of fibre-reinforced curable syntheticresin is placed over a core 3 of rectangular cross section over bothnarrow sides. The core 3 is composed for example of aluminium and issimilarly coated with a suitable agent to avoid adhesion of the profile4 and to render the core 3 removable after this. In its longitudinaldirection the configuration of the core 3 is adapted to theconfiguration of the supporting surface 1 in the longitudinal direction(normal to the plane of the drawing) of the latter. A plurality of theunits thus formed comprising the core 3 as well as two U-profiles 4 isplaced in spaced apart relationship onto the base layer 2. Thereafterone L-profile 5 each of fibre-reinforced curable reinforced syntheticresin is fitted along the transition between the base layer 2 and thebase portion 6 of the U-profile 4. A vacuum foil 7 is applied over thestructure thus formed and is adhesively bonded along the edges of thebase layer 2 onto the supporting surface 1. The space between the vacuumfoil 7 and the supporting surface 1 is subsequently evacuated. This isonce again followed by complete curing in an autoclave at a temperatureof 120° to 315° C., preferably 160°-282° C. and more preferably170°-200° C. and at a pressure of 4 to 10 bar. After curing, the vacuumfoil 7 and the core 3 are removed.

As illustrated in FIG. 2, the fully cured complete component accordingto FIG. 3 (or FIG. 1) may be provided with a covering 8 offibre-reinforced curable synthetic resin. Initially one rubber bag 9each having an inlet nipple 10 is inserted into each cavity between theU-profiles 4, to project beyond the end of the component. Thereafter thecovering 8 is applied onto the exposed limbs 11 of the U-profile 4. Avacuum foil 12 in the form of a bag is now drawn over the entireassembly such that the inlet nipples 10 project from the vacuum foil 12and are adhesively sealed in an airtight manner in their regions ofpassage 13. The space between the vacuum foil 12 and the rubber bags 9is now evacuated and complete curing of the covering 8 is conducted inan autoclave at the abovementioned temperatures and pressures, whilstpressure equilibration proceeds by way of the inlet nipples 10. Aftercomplete curing, the vacuum foil 12 and the rubber bags 9 are removed.

The aforegoing examples, read with the general description preceding it,will enable the person skilled in the art to practise all aspects of theinvention.

The claims which follow are to be considered an integral part of thepresent disclosure. Reference numbers (directed to the drawings) shownin the claims serve to facilitate the correlation of integers of theclaims, with illustrated features of certain preferred embodiments butare not intended to restrict in any way the language of the claims towhat is shown in the drawings, unless the contrary is clearly apparentfrom the context.

What we claim is:
 1. Component for cladding apertures in the fuselage ofan aircraft comprising a panel-like base layer, a plurality ofU-profiles and a plurality of L-profiles each having only two limbs atright angles to one another, said U-profiles each having a base portionand two limbs situated opposite each other and extending from oppositeends of the base portion, said U-profiles each being applied to saidbase layer with one of said limbs contacting the base layer and theU-profiles being parallel to each other, and wherein on one side of thebase portion of each of said U-profiles, which one side is opposite to aside from which the limbs extend, one of said L-profiles is located, onelimb of the L-profile being applied to the base layer and parallel tothe U-profiles, and the other limb of the L-profile being applied to thebase portion of the respective U-profile, the limbs of the U-profileswhich are at respective ends of the base layer pointing towards oneanother.
 2. Component according to claim 1, wherein the limbs of atleast some successive U-profiles are directed to face the limbs of anend profile.
 3. Component according to claim 1, wherein the limbs ofadjoining U-profiles face each other.
 4. Component according to claim 1,wherein a cover layer is applied onto the free standing limbs of theU-profiles, composed of fibre reinforced fully cured synthetic resin. 5.Component according to claim 1 wherein said base layer, said U-profiles,and said L-profiles are composed of fiber reinforced, fully curedsynthetic resin and are bonded together solely by thermal treatment atelevated pressure.
 6. Component according to claim 1 being removablelyconnected to the fuselage of the aircraft.
 7. Component according toclaim 5 being hingedly connected to the fuselage of the aircraft.